Add notes on DirAccess documentation

[BrianBHuynh]

Some notes are ported from FileAccess (for example file_exist) Other notes were added when needed (for example when included on the non static version but not on the static version) Other entirely new notes were added as well when required for example when getting a list of directories or if a directory exist or not

Clarified note at the top and made it more in line with the one found in file access

[BrianBHuynh]

Some of the notes are because of #99047 and similar issues. As shown in the minimum reproduction project the directories can just not exist inside the .pck file in some edge cases, and at the same time (like for FileAccess) files may not be included as well! These clarifications should make things more clear while in the editor, since although some were just copy and pasted from elsewhere, it will be easier for people using the engine to debug.

[BrianBHuynh]

Holy- you're fast LOL I was typing an addendum and saw you add the tags while I was about to press comment @>@ thanks for the review @Calinou

[BrianBHuynh]

:D radiant also helped me with some formating on the discord as well! Wanted to mention it since I'm not too familiar with adding them as a contributor on github

[Mickeon]

Not much of a fan of the sheer verbosity of these notes, but this information is important and it's better than not having it.

I could try to come up with different notes outright, but instead I'll just suggest tweaks in and there to mitigate this.

[BrianBHuynh]

O7 alright, I thought it'd be better to be verbose than not since it's confusing when something works in the editor but not outside of it (as compared to something that you can test in the editor)

[BrianBHuynh]

Just accepted and squashed most of those changes (I asked around just now and also personally think differ sounds better in this context than be different so that was the only one I didn't accept) @Mickeon

[BrianBHuynh]

There we go :D all neat and consistent now ✨

[Repiteo]

Thanks!